Certificate Key Matcher

We don't store your Private Keys and CSR on our servers.

What to Check?

Check if a Certificate and a Private Key match
Check if a CSR and a Certificate match

Paste Your Certificate Text

Paste Your Private Key

Paste Your CSR

About Certificate Key Matcher

Certificate and Private Key Matcher – Verify SSL Certificate and Key Pair

Verify SSL Certificate and Private Key Pair Online

The Certificate and Private Key Matcher tool checks if your SSL certificate matches its private key. A mismatch can cause web server errors and security risks. Our free online tool instantly checks if your certificate and key are a valid pair.

What Is an SSL Certificate-Key Pair?

An SSL certificate and a private key work together to secure online connections. When you get an SSL certificate, a private key is created too. If you don't use the original private key with the certificate, encryption won't work.

? Components:

• SSL Certificate: A public file from the CA that shows your domain's identity and encryption details.

• Private Key: A secret key on your server that decrypts messages encrypted by the public certificate.

How the Certificate-Key Matcher Works

The matcher checks the modulus and key fingerprint of both the SSL certificate and private key. It then compares them to see if they match.

✔️ Matching Criteria:

• The modulus of the certificate and the private key must be the same.

• The algorithm type (like RSA 2048-bit) must also match.

• Both keys must pass encryption and decryption tests.

Step-by-Step: Using the Certificate-Key Matching Tool

1. Paste the SSL Certificate in PEM format:

   cssCopyEdit-----BEGIN CERTIFICATE----- MIIDdzCCAl+gAwIBAgIEb0uZSz... -----END CERTIFICATE-----

2. Paste the Private Key in PEM format:

   vbnetCopyEdit-----BEGIN PRIVATE KEY----- MIIEvQIBADANBgkqhkiG9w0BAQ... -----END PRIVATE KEY-----

3. Click “Match” to check if they match instantly.

4. View Results:

   • ✅ Match Found: Your SSL certificate and private key pair correctly.

   • ❌ Mismatch: You'll be alerted to a mismatch issue.

Supported Key Types

Key Type	Bit Length	Supported
RSA	2048-bit, 4096-bit	✅
ECC	P-256, P-384	✅
DSA	2048-bit	✅ (Limited Use)

When and Why to Use a Key Matcher Tool

? SSL Troubleshooting

Use this tool when SSL installation fails due to "key mismatch" or "incomplete chain" errors. It quickly finds the root cause.

? Multiple CSRs or Certificates

If you've made multiple CSRs or got several certificates, it shows which private key matches which certificate.

? Security Assurance

It prevents misconfigured keys that can lead to unencrypted transmissions or SSL vulnerabilities.

? Web Hosting Setup

It's great for shared hosting, cPanel, or cloud environments where mismatched certificates are common.

Common Errors and How to Fix Them

Error Message	Cause	Resolution
Modulus mismatch	The private key is not the one used for the CSR	Reissue certificate using correct private key
Missing private key	Certificate generated but private key lost	Generate new CSR and private key, reapply for cert
Unsupported format	Key/certificate not in PEM format	Convert using OpenSSL tools

OpenSSL Conversion Example:

openssl rsa -in private.key -check openssl x509 -in certificate.crt -noout -modulus

Certificate-Key Match Validation Flow

flowchart TD A[Paste Certificate] --> C[Extract Modulus] B[Paste Private Key] --> D[Extract Modulus] C --> E[Compare Values] D --> E E -->|Match| F[Success ✅] E -->|No Match| G[Failure ❌]

Frequently Asked Questions (FAQs)

Is it safe to use this tool?

Yes. The process is secure in your browser. No data is sent or stored.

What formats are supported?

Only PEM is accepted. Convert other formats to PEM first.

Can I match intermediate certificates?

No. This tool is for end-entity (leaf) SSL certificates only.

Can I use this for expired certificates?

Yes. Expired certificates can be checked for diagnostic or migration.

Security Tips When Handling Private Keys

• Never share private keys over email or public networks.

• Use strong passwords and encryption when storing private keys.

• Limit access to private keys on your server to minimize breach risks.

Conclusion: Confirm Key-Certificate Compatibility Instantly

Verify your SSL installation with our free online matcher. It checks fast and ensures compatibility. It's vital for web admins, DevOps teams, and hosting pros.